Seals are well known made in general of elastic material and used in commercial applications to distinguish a variety of products. These seals are constituted in general by a rigid body provided with a flexible cord which at first is made to go through an opening, such as a slot, an eye or other opening provided in the article which must be marked and therefore anchored in a non-removable manner. The identification of the several articles is made by printing on the body of the seal specific data of the article such as the name or the nameplate of the party who produces the articles, the hoisting tackle, the code with bars and similar data. At present in commerce there are used seals made in great variety of shapes, dimensions and systems of reciprocal binding between the body and the flexible cord. By way of example, European Patent 0497795 should be mentioned because there is illustrated a seal comprising a perimetrical frame of rectangular shape made of thermoplastic material and provided with an internal cavity. On the body of the frame there is buried a small flexible cord which comes out from at least one of the two smaller sides and is provided at its ends with a spike which is going to be inserted in a non-removable manner on a corresponding opening made on the same side of the body.